The statistics scream average. The Celtics’ simple rating, a measurement of margin of victory and strength of schedule, is 16th out of 30 teams. Their net rating, the difference between points scored/allowed per 100 possessions, is 13th out of 30. Their expected record, which they’ve exceeded by a victory, is 11-11.

Both teams rank among the oldest in the league, with Boston (29.8 average years of age) at 27th and the Spurs (29.1) at 26th. But while the Spurs have been able stay fresh by rebuilding their supporting cast, the Celtics have struggled with that task.

Some had wondered before the season started if the Celtics might be the league’s deepest team with the additions of Jason Terry and Courtney Lee and Jeff Green’s return from injury. But while the Spurs rank second in bench efficiency, a formula that measures the total sum of production, the Celtics languish in 22nd. Green has been especially disappointing, averaging just 10 points with a 11.9 Player Efficiency Rating.

Despite the lack of support, Boston’s core of Kevin Garnett, Paul Pierce and Rajon Rondo remains strong. If not quite as good as Tim Duncan by most measures, Garnett (15.9 ppg) is likewise an All-Star candidate in his 16th season. Indeed, he ranks just ahead of Garnett in fourth with a 6.3 Regularized Adjusted Plus/Minus. Pierce (19.8 ppg) is leading the Cs in scoring once again at 35, and Rondo 12.9 apg) is on pace for his second straight assists title.

No other Celtic has a better than average PER, and that’s about as telling a measure as any of a team battling to stem the ravages of time.

Injury report

PG Avery Bradley (shoulder), out.

What to watch

* Rondo’s reputation as a poor jump shooter is no longer accurate. He’s made 54 percent of his attempts from 16-23 feet, fourth-highest among players who take at least three such shots per game. His improved outside stroke is a major reason why he’s shooting a career-best 51.8 percent overall.

* Having moved to center full-time, Garnett remains among the NBA’s most impactful defenders. The Celtics’ defensive rating swells from 93.2 – which would league the league if applied for a full game – to 111.1 when he leaves the court, one of the largest disparities in the league.

* While generally decent on defense, the Celtics struggle mightily on the interior, allowing 43 points in the paint per game to rank 4th. They’re bizarrely inconsistent against the pick and roll, allowing the fewest points per play decided by ballhanders but 29th in those finished by the roll man.